/*
 * Copyright 2002-2016 the original author or authors.
 *
 * Licensed under the Apache License, Version 2.0 (the "License");
 * you may not use this file except in compliance with the License.
 * You may obtain a copy of the License at
 *
 *      https://www.apache.org/licenses/LICENSE-2.0
 *
 * Unless required by applicable law or agreed to in writing, software
 * distributed under the License is distributed on an "AS IS" BASIS,
 * WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
 * See the License for the specific language governing permissions and
 * limitations under the License.
 */

package org.springframework.test.web.servlet.setup;

import org.springframework.util.Assert;
import org.springframework.web.util.UrlPathHelper;

import javax.servlet.*;
import javax.servlet.http.HttpServletRequest;
import java.io.IOException;
import java.util.ArrayList;
import java.util.List;

/**
 * A Filter that invokes a delegate {@link Filter} only if the request URL
 * matches the pattern it is mapped to using pattern matching as defined in the
 * Servlet spec.
 *
 * @author Rob Winch
 * @since 3.2
 */
final class PatternMappingFilterProxy implements Filter {

    private static final String EXTENSION_MAPPING_PATTERN = "*.";

    private static final String PATH_MAPPING_PATTERN = "/*";

    private static final UrlPathHelper urlPathHelper = new UrlPathHelper();

    private final Filter delegate;

    /**
     * Patterns that require an exact match, e.g. "/test"
     */
    private final List<String> exactMatches = new ArrayList<>();

    /**
     * Patterns that require the URL to have a specific prefix, e.g. "/test/*"
     */
    private final List<String> startsWithMatches = new ArrayList<>();

    /**
     * Patterns that require the request URL to have a specific suffix, e.g. "*.html"
     */
    private final List<String> endsWithMatches = new ArrayList<>();


    /**
     * Creates a new instance.
     */
    public PatternMappingFilterProxy(Filter delegate, String... urlPatterns) {
        Assert.notNull(delegate, "A delegate Filter is required");
        this.delegate = delegate;
        for (String urlPattern : urlPatterns) {
            addUrlPattern(urlPattern);
        }
    }

    private void addUrlPattern(String urlPattern) {
        Assert.notNull(urlPattern, "Found null URL Pattern");
        if (urlPattern.startsWith(EXTENSION_MAPPING_PATTERN)) {
            this.endsWithMatches.add(urlPattern.substring(1, urlPattern.length()));
        }
        else if (urlPattern.equals(PATH_MAPPING_PATTERN)) {
            this.startsWithMatches.add("");
        }
        else if (urlPattern.endsWith(PATH_MAPPING_PATTERN)) {
            this.startsWithMatches.add(urlPattern.substring(0, urlPattern.length() - 1));
            this.exactMatches.add(urlPattern.substring(0, urlPattern.length() - 2));
        }
        else {
            if ("".equals(urlPattern)) {
                urlPattern = "/";
            }
            this.exactMatches.add(urlPattern);
        }
    }


    @Override
    public void doFilter(ServletRequest request, ServletResponse response, FilterChain filterChain)
            throws IOException, ServletException {

        HttpServletRequest httpRequest = (HttpServletRequest) request;
        String requestPath = urlPathHelper.getPathWithinApplication(httpRequest);

        if (matches(requestPath)) {
            this.delegate.doFilter(request, response, filterChain);
        }
        else {
            filterChain.doFilter(request, response);
        }
    }

    private boolean matches(String requestPath) {
        for (String pattern : this.exactMatches) {
            if (pattern.equals(requestPath)) {
                return true;
            }
        }
        if (!requestPath.startsWith("/")) {
            return false;
        }
        for (String pattern : this.endsWithMatches) {
            if (requestPath.endsWith(pattern)) {
                return true;
            }
        }
        for (String pattern : this.startsWithMatches) {
            if (requestPath.startsWith(pattern)) {
                return true;
            }
        }
        return false;
    }

    @Override
    public void init(FilterConfig filterConfig) throws ServletException {
        this.delegate.init(filterConfig);
    }

    @Override
    public void destroy() {
        this.delegate.destroy();
    }

}
